Tunnel magnetoresistance and robust room temperature exchange bias with multiferroic BiFeO3 epitaxial thin films

TLDR

The study focuses on functionalizing multiferroic BiFeO₃ epitaxial films for spintronic applications. They use ultrathin BiFeO₃ layers as tunnel barriers in MTJs with La₂⁄₃Sr₁⁄₃MnO₃ and Co electrodes, and exploit its antiferromagnetic spin structure to induce a sizable exchange bias on CoFeB at room temperature. The devices exhibit a positive tunnel magnetoresistance of up to 30 % at low temperature and a robust room‑temperature exchange bias (~60 Oe) on CoFeB that persists through magnetic field cycling without training.

Abstract

The authors report on the functionalization of multiferroic BiFeO3 epitaxial films for spintronics. A first example is provided by the use of ultrathin layers of BiFeO3 as tunnel barriers in magnetic tunnel junctions with La2∕3Sr1∕3MnO3 and Co electrodes. In such structures, a positive tunnel magnetoresistance up to 30% is obtained at low temperature. A second example is the exploitation of the antiferromagnetic spin structure of a BiFeO3 film to induce a sizable (∼60Oe) exchange bias on a ferromagnetic film of CoFeB at room temperature. Remarkably, the exchange bias effect is robust upon magnetic field cycling, with no indications of training.